A Novel Approach for Warhead Fragments Velocity Measurement Based on Laser Screen

The velocity of warhead fragment is key criteria to determine its mutilation efficiency.We have designed an optoelectronic system to accurately measure the average velocity of warhead fragments.The apparatus including two parallel laser screens spaced apart at a known fixed distance for providing time measurement start and stop signals.The large effective screen area is formed by laser source,retro-reflector and large area photo-diode with a central hole.Whenever a moving fragment interrupts two optical screen,the corresponding photometers senses the event,due to partial obscuration of the incident energy.Experiments have been performed to measure velocity of the different kinds of projectiles and fragments within various size and velocity ranges,including 7.62 mm bullet shooting experiments,prefabricated steel-ball exploding experiments.They were proved that the system is adequate to measure the velocity of larger than 5 mm,less than 1 000 m/s in the range,when fixed trajectory,test the velocity of the projectile average relative deviation is less than 4.21%.The system can perform satisfactorily with a lot of advantages such as larger effective light screen area,quick response speed,low uncertainty,strong repetition and reliability,etc.

Study on Coaxiality Measurement System of Compound Gear Shaft Based on Non⁃contact Optic

Aiming at the shortcomings of traditional contact measurement methods such as low measurement efficiency,high cost and low accuracy,a non-contact optical measurement method based on the laser displacement sensor is proposed.According to the relevant regulations of the coaxiality error evaluation standard and the structural characteristics of the compound gear shaft,we have designed and built a set of supporting software system as well as a hardware test platform.In this paper,the distance difference threshold and scale threshold methods are used to eliminate outlier data.The least squares circle is selected to calculate the center of the circle and the minimum containment cylinder axis method is used as the reference axis of the composite gear shaft.Compensated by the standard step shaft calibration,the coaxiality error of the composite gear shaft can be measured to be within 0.01 mm in less than two minutes.The range value of the multi-section measurement test is 0.065 mm.The average coaxiality error is∅0.476 mm.

Clinical study using novel endoscopic system for measuring size of gastrointestinal lesion

AIM: To verify the performance of a lesion size measurement system through a clinical study.

Non-Contact Measurements of Water Jet Spreading Width with a Laser Instrument

Jet spreading width is one of the important characteristics of water jets discharging into the air.Many researchers have dealt with measuring this width,and contact measuring methods on the water jet surface were employed in a lot of the cases.In order to avoid undesirable effects caused by the contact on the jet surface,we introduce non-contact measuring methods with a laser instrument to the measurements of jet spreading width.In measurements,a transmitter emits sheet-like laser beam to a receiver.The water jet between the transmitter and the receiver interrupts the laser beam and makes a shadow.The minimum and maximum values of the shadow width are measured.In addition,pictures of the water jet are taken with a scale,and the shadow width is measured from the pictures.The experiments on various needle strokes were performed.Three kinds of width consistent with the jet structure were obtained.In the results,it can be concluded that our non-contact measuring methods are feasible.The data of jet spreading widths and jet taper were obtained and are useful for future applications.

Identification of Internal Damage in Circular Cylinders through Laser Scanning of Vibrating Surfaces

With the aid of non-contact measurements of vibrating surfaces through laser scanning,operating deflection shapes(ODSs)with high spatial resolutions can be used to graphically characterize damage in plane structures.Although numerous damage identification approaches relying on laser-measured ODSs have been developed for plate-type structures,they cannot be directly applied to circular cylinders due to the gap between equations of motions of plates and circular cylinders.To fill this gap,a novel approach is proposed in this study for damage identification of circular cylinders.Damage-induced discontinuities of the derivatives of ODSs can be used to gra-phically manifest the occurrence of the damage,and characterize the location and size of the damage.The approach is experimentally validated on a specimen of the circular cylinder component,whose out-of-plane ODSs in an inspection region are acquired through laser scanning using a scanning laser vibrometer.The results suggest that the occurrence,location,and size of the internal damage of the circular cylinder can be identified.

Non-contact optical dynamic measurements at different ranges:a review

Optical dynamic measurements are widely used for non-contact vibration,continuous deformation,or moving objects.Various measurement techniques were developed for different deformation amplitudes.This paper reviews three types of technique for different measurement ranges:interferometric techniques for deformation or vibration(nanometer to submillimeter amplitude)whose measurement accuracies rely on phase extraction of interferometric signal;imaging based techniques for deformation or vibration(micrometer to centimeter amplitude)with the aid of moire,structured light,and man-made speckles,whose sensitivities is from 1/100 to 1/10 pixel;and videometrics for large deformation or movement detection(greater than centimeter amplitude).Many research groups have improved measurement capabilities for these three techniques to meet particular industrial application requirements.

Rail Flatness and Verticality Measurement System Based on Ruler Model

Currently,the manual contact rail measurement that was basically adopted in China has low detection efficiency,poor accuracy and poor stability.In order to improve the function of the system,we propose a non-contact measurement method based on the flatness and verticality ruler model.The flatness measurement model was built by employing the string measurement method.In addition,the verticality measurement model was built by the dihedral method to measure the rail comprehensively.By extracting curvature information of feature points,in this system,each laser sensor is used to collect rail profile curves.A large number of three-dimensional point clouds data are generated by the unit quaternion method of coordinate transformation,and the contour curves of the characteristic points of the four laser sensors are matched with the corresponding point sets one to one,and the rail contour splicing is finally completed.The experimental results show that this method has better measurement effect compared with the traditional manual measurement method.

Novel laser Doppler tachometer

In order to improve the accuracy and universality of the rotational speed measurement,an instantaneous rotational speed measurement method based on laser Doppler technology is proposed.The composition and working principle of the new system are discussed in detail.Theoretical and experimental results show that the new rotational speed measurement system belongs to the non-contact method,which eliminates the quantization error of the contact method and greatly improves the applicability and accuracy.Compared to the commonly used method,the measurement accuracy of the new rotational speed measurement system will not be affected by the system’s installation angle deviation,and it does not need to measure the radius of the rotating body,so the influence of the radius fluctuation of the rotating body on the measurement accuracy can be avoided while outputting the rotational speed in real time.The relative error of the rotational speed measurement is less than 0.06%(1σ).